class Solution
{
public:
    int combinationSum4(vector<int>& nums, int target)
    {
        vector<unsigned long long> dp(target + 1);
        dp[0] = 1;
        for (int i = 1; i <= target; i++)
        {
            for (auto x : nums)
            {
                if (i >= x)
                    dp[i] += dp[i - x];
            }
        }
        return dp[target];
    }
};